Absolutely this. If the players accept that they're playing a game, rather than playing their characters, then it changes everything. My group only ever suffers from the 5MWD issue during travel, and the solution to that has been to have most wilderness combat either be a side-trek adventure or a super-deadly fight where they NEED to go nova. During most adventures, they ration their resources (although they do tend to nova against the perceived BBEG) because they don't know how long they need to go.I think the 5mwd is more a problem of style of play rather than mechanic.
if players focus on their character being hero on mission or adventuring, they will
do their best with their ressource, and eventually look for a long rest.
if players focus on their character sheet, spells, abilities, they will play accordingly to that.
DnD assume that players will willingly try to impersonate a hero and play accordingly to that.
expecting that the rules force players to do that is asking too much.
Case in point with my current group (I'm a player in this session). Last week we were investigating some cultists. We found their hidden lair, and were exploring it, killing off all the cultists we came across. However, we had one bad encounter that left us quite injured and with only 1 wizard spell (cleric and bard were empty), 2 bardic inspirations, and about half our HP remaining. We continued exploring, hoping there wasn't anyone left, but our scout ran across a lone cultist. We discussed if we should move to attack, or if we should withdraw entirely. We decided that attacking was the better choice, since if we withdrew, she would know what we'd done, and would likely either flee to another location or summon reinforcements when we returned. Needless to say, she was the cult's leader, and nearly killed all of us (2 of 5 PCs remained standing, both with 1 HP received from natural 20s on death saves).